High-pressure, supplied-air respirators are given an Assigned Protection Factor of 25 by NIOSH. What does this 25 mean?

The wearer can be exposed to particulates of 25 microns or smaller.
The wearer can be exposed to breathable material above its OSHA Permissible Exposure Limit for 25 minutes before exiting the exposure zone for at least 10 minutes.
The wearer can be exposed to contaminants in a concentration of up to 25 times OSHA’s Permissible Exposure Limit.
None of these